Defrosting refrigeration cycle



United States Patent 065cc Patented Sept. 20, 1955 DEFRGSTING REFRIGERATIGN CYCLE Ray 0. Wiley, Omaha, Nehru, assignor to Wilkinson Manufacturing Company, Omaha, Nebr., a corporation of Nebraska Application November 16, 1953, Serial No. 392,192

5 Claims. (Cl. 62--3) This invention relates generally to refrigeration systerns, and more particularly to automatic temperature control and the use of hot compressor discharge gas for defrosting purposes.

This invention is intended for use with unitary air conditioning or refrigeration apparatuses of the type employed to heat or refrigerate a confined space, such as the interior of a truck, railroad car, or similar carrier in the manner and for the objects disclosed with arrangements of the type generally described in Arkoosh et a1. application Serial No. 226,262, and Wiley application Serial No. 280,755.

It is a primary object of the present invention to provide a mechanism which is automatically operable to heat or cool a confined space, and to maintain the temperature therein within a predetermined range.

it is another object of the present invention to provide a refrigeration system having automatic temperature regulation operative to initiate defrosting or heating in response to pressure conditions within the system.

It is a further object of the present invention to pro vide a refrigeration system automatically responsive to temperature conditions outside the system, and pressure conditions within the system, to maintain the temperature of a confined space to be cooled within predetermined limits.

It is still another object of the present invention to provide a refrigeration system employing by-pass of hot compressor gases to the evaporator to 'efiect defrosting in response to pressure conditions within the system.

With these and other obejcts in view, my invention consists in the construction, arrangement and combination of the various parts of my defrosting refrigeration cycle whereby the objects contemplated are obtained as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawing, wherein:

Figure 1 is a schematic layout of a refrigeration system embodying the present invention.

Figure 2 is a wiring diagram for the refrigeration system of Figure 1, showing the cooperative relation of various control devices and switch arrangements.

Referring more particularly to Figure l of the drawing, I have shown a schematic layout 'of a refrigeration system embodying the features of the present invention. A compressor 10, having an intake side 12 and a discharge side 14-, is suitably connected to an auxiliary engine 16 to be driven thereby. The .engine 16 may be of the gasoline driven internal combustion type having an electrical starter device 17 adapted to .be actuated by a suitable source of power such as a storage battery 18 and operatively connected within a control circuit, C, to an ignition means 19.

An evaporator 20 comprising a cooling coil 22, and having an inlet 24 and an outlet 25, is connected to the compressor by means of a suction line 26. The line 26 communicates at its one end with the outlet of the evaporator 20, and at its other end with the intake side 12 of the compressor ll).

A condenser 30 comprising a tubular coil 32, and having an inlet 34 and an outlet 35, is connected to the compressor by means of a gas line 36. The line 36 communicates at its one end with the inlet 34 of the condenser 30, and at its other end with the discharge side 14 of the compressor 10. A solenoid actuated check valve 38 is positioned in the line 36 adjacent the inlet 34 to disconnect the condenser 30 from the line 36.

The outlet of the condenser communicates with a receiver tank 40. A liquid line 42 connects the receiver tank to the inlet 24 of the evaporator 20. An expansion valve 44 is suitably positioned in the line 40 adjacent the evaporator inlet 24. A solenoid actuated valve 46 is positioned in the liquid line 42 between the receiver tank 40 and the expansion valve 44.

A by-pass line 50 is provided between the gas line 36 and the liquid line 42. The line 50 is connected at its one end to the gas line 36 at a point between the discharge side 14 of the compressor 10 and the check valve 38, and at its other end to the liquid line 42 at a point between the inlet 24 of the evaporator 20 and the eXpansion valve 44. A solenoid valve 52 is positioned in the by-pass line 50 to control the flow therethrough.

A pressure responsive control device is operatively connected at the intake side of the compressor 10 to sense the relatively low pressure in the suction line 26. The low pressure control 60 is suitably connected to the valves 52 and 38 by means of an electrical control circuit which will hereinafter be described in detail, to effect opening and closing thereof in a novel manner in response to predetermined pressure conditions between the evaporator 20 and the compressor 10.

A second pressure responsive control device is operatively connected at the discharge side of the compressor 10 to sense the relatively high pressure in the gas line 36. The high pressure control 70 operates in response to a predetermined high pressure to effect a closing of the valve 46, in liquid line 42, so as to interrupt the cooling operation of the system, whereby the continued operation of the compressor serves to relieve any excessive pressures which may have been built up by the system.

Referring now more particularly to Figure 2 of the drawing, I have shown a diagram of the control circuit whereby the refrigeration system heretofore described may be regulated in accordance with the novel method of the present invention.

Switch 81 is a double pole single throw switch which is initially in a normally closed position so as to connect the pressure responsive control devices 60 and 70 to a source of power, indicated herein as being storage battery 18. The switch 81 also serves to connect an ignition system of conventional type to the battery 18 for the purpose of maintaining operation of the internal combustion engine 17.

The high pressure control device 70 is operative to position a single pole double throw switch 82. The

switch 82 can be adjusted for either automatic or manual system operation. By providing circuit connection to a contact post 82a, a thermostatic control device '90 is introduced for the purpose of automatically opening and closing the valve 46 in response to temperature conditions independent of the pressure responses of control 70. Alternative connection of the switch 82 to another contact post 82b serves to eliminate the thermostatic control from the circuit, and permits manual controlof the cooling system.

The control 70 is operative in response to excessively high pressures at the discharge side of the compressor to effect a closing off of the valve 46, which permits the continued operation of the system to lower the pressure in suction line 26 and in turn lower the high pressure in gas control device 90.

line 36. In this manner, the cooling operation is interrupted and the system is effectively protected against excessive pressures.

The switch 82 can also be centered between posts 82a and 8212 so as to allow the system to reach a pressure predetermined by setting of the low pressure control 60. In response to such a predetermined pressure, the control 60 operates to effect an opening of the by-pass valve 52 to permit circulation of hot discharge gas through the evaporator 20. Such circulation continues until the switch 82 is moved to a contact position.

A single pole single throw switch 83 operates as a defrost switch. The switch 83 is normally open, and may be closed either manually, or automatically in response to control device 60, to open the normally closed by-pass valve 52.

A double pole single throw momentary contact switch 84 is provided for manual starting of the system. The switch 34 serves to connect the starter 17 to the battery 18, thereby energizing the starter to initiate operation of the motor 16. The switch 84 also serves to connect the solenoid of by-pass valve 52 to the power source 18 and effect an opening of the valve. In this manner, the motor 16 is started against an unloaded cooling system. Since the switch 84 is of the momentary contact type, the starter becomes inactive, and the valve 52 returns to its closed position, after the brief interval during which contact is maintained by the switch 84 to effect starting of the motor 16.

Operation of the refrigeration system of the present invention is generally effected in the following manner. The system is first actuated by the switch 84, which serves to energize the starter 17 and initiate operation of the motor 16. With the compressor running, the coolant liquid Will be circulated through the system in accordance with the usual sequence of operations of a conventional refrigeration cycle. The cooling operation of the system may then be regulated either manually or in response to temperature conditions serving to actuate the thermostatic When the solenoid actuated valve 46 is closed in response to thermostatic or manual control, the continuing operation of the compressor will serve to pump liquid and gas out of the cooling coil 20, until a predetermined pressure has been reached in the line 26. The low pressure control device 60 will respond to the predetermined condition in the line 26 so as to effect an opening of the solenoid actuated valve 52 thereby allowing hot compressor discharge gas to circulate through the cooling coil 22. In this manner, defrosting or temperature control, or heating, may be accomplished.

During ordinary continuous operation of the present refrigeration system, frost or ice will tend to form upon the coil 22 of the evaporator 20. When such frost formation has built up an ice layer of substantial thickness upon the coil 22, heat transfer from the surroundings through the walls of the coil to the refrigerant fluid therein will be materially reduced. Such an insulating layer of ice upon the evaporator coil, and consequent lowered heat transfer therethrough, will cause the pressure in suction line 26 to decrease. When the pressure in line 26 has dropped to a given predetermined value, the low pressure control device 60 will respond to effect an opening of the by-pass valve 52, thereby circulating hot compressor gas through coil 22 and effecting a defrosting of the ice formed thereon.

Simultaneous closure of the check valve 38 with the opening of the bypass valve 52 serves to retain gas and liquid in the condenser coil 30 during such a defrosting or heating cycle. When valve 46 is again opened, in response to a pressure increase in the line 26 due to re-cycling compressor gases, liquid will once again be circulated from the receiver tank 46 to the evaporator 20. The consequent pressure rise in the cooling coil 22 will effect an actuation of the control 60 to close the by-pass valve 52,

thereby allowing the system to return to its initial function on a cooling cycle.

It should be noted that control 60 may be adjusted to allow the pressure within the evaporator 21 to reach a certain predetermined pressure before allowing the bypass valve 52 to be opened for circulating hot gas from the compressor through the evaporator coil 22. By properly adjusting the pressure differential to which the control 60 will respond, the pressure and temperature in the evaporator will be permitted to rise, thereby effecting defrosting even though the valve 46 remains open. In this manner, automatic defrosting may be accomplished.

The high pressure control device 7% may be adjusted to respond to excessively high pressure within the system to close the valve 46 and allow the continued operation of the cooling system to lower the pressure on the suction side of the compressor, line 26, which in turn serves to lower the high pressure on the discharge side, line 36, to protect the system against excessive pressure by causing interrupted cooling.

Changes may be made in the construction and arrangement of the parts of my defrosting refrigeration system without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical improvements which may be reasonably included within their scope.

I claim:

1. In a refrigeration system including a gas compressor, an evaporator, a suction line connecting the outlet of said evaporator to the intake side of said compressor, a condenser, a gas line connecting the inlet of said condenser to the discharge side of said compressor, a liquid line connecting the outlet of said condenser to the inlet of said evaporator, and a by-pass line between the discharge side of the compressor and the inlet side of the evaporator, the improvements comprising valve means in said by-pass line, pressure responsive control means operatively positioned at the intake side of said compressor and operatively connected to said valve means to open and close said valve means in response to predetermined pressures in said suction line, whereby hot gas is intermittently circulated from said compressor to said evaporator, and valve means in said liquid line operatively independent of pressures in said suction line, whereby closing of said liquid line valve means effects actuation of said by-pass line valve means.

2. In a refrigeration system including a gas compressor, an evaporator, a suction line connecting the outlet of said evaporator to the intake side of said compressor, a condenser, a gas line connecting the inlet of said condenser to the discharge side of said compressor, a liquid line connecting the outlet of said condenser to the inlet of said evaporator, and a by-pass line between the discharge side of the compressor and the inlet side of the evaporator, the improvements comprising valve means in said bypass line, pressure responsive control means operatively positioned at the intake side of said compressor and operatively connected to said valve means to open and close said valve means in response to predetermined pressures in said suction line, whereby hot gas is intermittently circulated from said compressor to said evaporator, and a check valve in said gas line between said by-pass line and said condenser, said pressure responsive control means being operatively connected to said check valve to close and open said valve upon opening and closing of said by-pass line valve means.

3. In a refrigeration system including a gas compressor, an evaporator, a suction line connecting the outlet of said evaporator to the intake side of said compressor, a condenser, a gas line connecting the inlet of said condenser to the discharge side of said compressor, a liquid line connecting the outlet of said condenser to the inlet of said evaporator, and a by-pass line between the discharge side of the compressor and the inlet side of the evaporator, improvements comprising a first valve means in said by-pass line, pressure responsive control means operatively positioned at the intake side of said compressor and operatively connected to said first valve means to eifect opening and closing thereof in response to predetermined pressures in said suction line, and second valve means in said liquid line, whereby closure of said second valve means during continuing operation of said compressor serves to eflect a pressure change in said suction line thereby actuating said pressure responsive control means to open said first valve and circulate hot gas from said compressor to said evaporator.

4. In a refrigeration system including a gas compressor, an evaporator, a suction line connecting the outlet of said evaporator to the intake side of said compressor, a condenser, a gas line connecting the inlet of said condenser to the discharge side of said compressor, a liquid line connecting the outlet of said condenser to the inlet of said evaporator, and a by-pass line between the discharge side of the compressor and the inlet side of the evaporator, improvements in temperature control comprising first valve means in said by-pass line, first control means responsive to predetermined pressures in said suction line and operative to open and close said first valve means, second valve means in said liquid line, and second control means operative to open and close said second valve means, whereby closure of said second valve means during continuing operation of said compressor effects a decrease of pressure in said suction line causing said first control means to open said first valve means and circulate hot gas from said compressor to said evaporator.

5. In a refrigeration system including a gas compressor, an evaporator, a suction line connecting the outlet of said evaporator to the intake side of said compressor, a condenser, a gas line connecting the inlet of said condenser to the discharge side of said compressor, a liquid line connecting the outlet of said condenser to the inlet of said evaporator, and a by-pass line between the discharge side of the compressor and the inlet side of the evaporator, improvements in temperature control comprising first valve means in said by-pass line, first control means responsive to predetermined pressures in said suction line and operative to open and close said first valve means, second valve means in said liquid line, and second control means operative to open and close said second valve means, whereby closing and opening of said second valve means during continuing operation of said compressor efiects pressure variations in said suction line causing said first control means to intermittently open and close said valve means in response to predetermined pressures thereby circulating hot gas from said compressor to said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 2,313,390 Newton Mar. 9, 1943 2,433,574 Newton Dec. 30, 1947 2,451,385 Groat Oct. 12, 1948 2,451,682 Lund Oct. 18, 1948 

